排序方式： 共有78条查询结果，搜索用时 31 毫秒
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提出了多频分量相位演化零点时间的概念.对于复杂非平稳地震动过程,为降低求解多频分量相位演化零点时间的工作量,引入地震波波群演化的思想,在地震波相位谱敏感性分析的基础上,考察了典型实测地震动时程的模拟.结果表明,拟合地震动过程与实测非平稳地震动吻合较好,本文提出的相位谱重构方法具有重要的实践意义.同时,这一方法也为非平稳... 相似文献
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非平稳地震信号匹配追踪时频分析 总被引：1，自引：0，他引：1
根据三步法匹配追踪原理实现了基于雷克子波的地震信号自适应分解,在此基础上,讨论了利用匹配子波进行地震信号时频表征的方法。由于常规匹配追踪时频是以Wigner-Ville分布为基础,得到的时频信息有限,因此给出了一种基于可调窗口的短时傅氏变换时频表示方法,进而又利用各匹配子波的复谱,引入一种新的时频表示方法,不仅与Wigner-Ville方法具有同等的分辨率和能量聚集特性,而且保留了原信号的最基本时频特征,不存在交叉项和窗口截断效应。通过与短时傅氏变换和S变换时频特征的对比发现,匹配追踪时频表征和瞬时谱参数具有更高的分辨率。实际数据的应用也表明,匹配追踪分解非常适用于非平稳特征的地震信号的时频分析。 相似文献
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合肥市商业地价驱动因素的空间非平稳性分析 总被引：2，自引：1，他引：1
基于微观因素的视角,对合肥市商业地价的空间格局、空间异质性进行空间插值和回归分析,研究发现： ① 商业地价空间格局呈现多中心的结构,峰值区集中分布在城市中心,低值区分布在二环线以外的地区;② GWR模型能清晰地反映出各因素对地价影响力的空间差异,容积率、交通站点、CBD和公园是研究区商业地价的关键驱动因素;③ 较之外在因素,内在因素对商业地价的边际作用效率较大,其中尤以容积率最为突出;④ 相较于欠发达地区,容积率在高度发达的区域对地价的正向效应更为显著,而交通站点和CBD对地价的作用正好相反。商业开发更愿意为小型公园支付更高的价格。 相似文献
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ABSTRACTThe main sources of uncertainty in the soil specification and mechanical behaviour consist of the lithological and heterogeneous randomness of soil deposits. It is quite obvious that the cone penetration testing (CPT) data and the variation of soil characteristics are not stationary. Hence, this paper investigates a new approach to realise a CPT data, taking both sources of uncertainty into consideration. In this regard, the first part of this study illustrates a simple approach to stratify the CPT data, using the Eslami–Fellenius chart of classification. In the second part, the non-stationary algorithm of generating random field is introduced to generate a multi-layer random field. This algorithm takes account of each layer’s statistical properties (i.e. standard deviation, mean, and the trend value), separately. To validate the proposed approach, 41 case histories from different worldwide sites, have been regenerated by considering both the stationary and non-stationary algorithms. The correlation coefficient between real and realised CPT data has been employed to show that the proposed non-stationary algorithm can simulate the CPT data more accurately in comparison with the stationary algorithm. 相似文献
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This paper investigated spatiotemporal dynamic pattern of vegetation, climate factor, and their complex relationships from seasonal to inter-annual scale in China during the period 1982–1998 through wavelet transform method based on GIMMS data-sets. First, most vegetation canopies demonstrated obvious seasonality, increasing with latitudinal gradient. Second, obvious dynamic trends were observed in both vegetation and climate change, especially the positive trends. Over 70% areas were observed with obvious vegetation greening up, with vegetation degradation principally in the Pearl River Delta, Yangtze River Delta, and desert. Overall warming trend was observed across the whole country (>98% area), stronger in Northern China. Although over half of area (58.2%) obtained increasing rainfall trend, around a quarter of area (24.5%), especially the Central China and most northern portion of China, exhibited significantly negative rainfall trend. Third, significantly positive normalized difference vegetation index (NDVI)–climate relationship was generally observed on the de-noised time series in most vegetated regions, corresponding to their synchronous stronger seasonal pattern. Finally, at inter-annual level, the NDVI–climate relationship differed with climatic regions and their long-term trends: in humid regions, positive coefficients were observed except in regions with vegetation degradation; in arid, semiarid, and semihumid regions, positive relationships would be examined on the condition that increasing rainfall could compensate the increasing water requirement along with increasing temperature. This study provided valuable insights into the long-term vegetation–climate relationship in China with consideration of their spatiotemporal variability and overall trend in the global change process. 相似文献
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中国亚热带丘陵山区植被沿海拔梯度分布格局(英文) 总被引：3，自引：0，他引：3
Knowledge of vegetation distribution patterns is very important.Their relationships with topography and climate were explored through a geographically weighted regression(GWR) framework in a subtropical mountainous and hilly region,Minjiang River Basin of Fujian in China.The HJ-1 satellite image acquired on December 9,2010 was utilized and NDVI index was calculated representing the range of vegetation greenness.Proper analysis units were achieved through segregation based on small sub-basins and altitudinal bands.Results indicated that the GWR model was more powerful than ordinary linear least square(OLS) regression in interpreting vegetation-environmental relationship,indicated by higher adjusted R 2 and lower Akaike information criterion values.On one side,the OLS analysis revealed dominant positive influence from parameters of elevation and slope on vegetation distribution.On the other side,GWR analysis indicated that spatially,the parameters of topography had a very complex relationship with the vegetation distribution,as results of the various combinations of environmental factors,vegetation composition and also anthropogenic impact.The influences of elevation and slope generally decreased,from strongly positive to nearly zero,with increasing altitude and slope.Specially,most rapid changes of coefficients between NDVI and elevation or slope were observed in relatively flat and low-lying areas.This paper confirmed that the non-stationary analysis through the framework of GWR could lead to a better understanding of vegetation distribution in subtropical mountainous and hilly region.It was hoped that the proposed scale selection method combined with GWR framework would provide some guidelines on dealing with both spatial(horizontal) and altitudinal(vertical) non-stationarity in the dataset,and it could easily be applied in characterizing vegetation distribution patterns in other mountainous and hilly river basins and related research. 相似文献
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Earthquake probability prediction is based on earthquakes occurred in a certain seismo-tectonic region topredict the probable times and probability of certain magnitude segment earthquake or the earthquake whose mag-nitude is larger than certain magnitude low limit in the coming certain period, this was extensively applied toearthquake risk analysis and earthquake forecast.…… 相似文献
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基于EMD的信号瞬时特征的小波分析方法 总被引：8，自引：1，他引：7
提出了一种基于EMD(Empirical Mode Decomposition)的信号瞬时特征的小波分析方法。用这种方法提取非平稳信号的瞬时频率和瞬时幅值分三个基本步骤：首先,用EMD把信号分解成IMF(Intrinsic Mode Function)分量;接着,对IMF分量进行小波分析,从小波系数的幅角函数中提取小波脊线;最后,从小波脊线中提取瞬时频率和瞬时幅值。通过对仿真信号的分析,验证了该方法能有效地分析非平稳信号。 相似文献
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